Single-species dinoflagellate cyst carbon isotope ecology across the Paleocene-Eocene Thermal Maximum

Appy Sluijs,Gert-Jan Reichart,Jelmer Laks,Joost Frieling,Linda Van Roij

doi:10.1130/g39598.1

Appy Sluijs, Gert-Jan Reichart + Show 3 more

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https://doi.org/10.1130/g39598.1

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Abstract

We present the first ever species-specific fossil dinoflagellate cyst stable carbon isotope (δ13C) records, from the Bass River Paleocene- Eocene Thermal Maximum (PETM) section in New Jersey (USA), established using a novel coupled laser ablation- isotope ratio mass spectrometer setup. Correspondence with carbonate δ13C records across the characteristic negative carbon isotope excursion indicates that the δ13C of dissolved inorganic carbon exerts a major control on dinocyst δ13C. Pronounced and consistent differences between species, however, reflect different habitats or life cycle processes and different response to pCO2. Decreased interspecimen variability during the PETM in a species that also drops in abundance suggests a more limited niche, either in time (seasonal) or space. This opens a new approach for ecological and evolutionary reconstructions based on organic microfossils.

Highlights

Fossilizable organic cyst–producing dinoflagellates are ecologically diverse unicellular eukaryotes, and include freshwater and marine, heterotrophic, mixotrophic, autotrophic, and polar and tropical species (Matthiessen et al, 2005)
Individual dinocysts of the species Apectodinium homomorphum, Areoligera volata, Spiniferites ramosus, and Eocladopyxis peniculata were pressed on a nickel sample tray, which was placed in a miniaturized ablation chamber
Small peak areas correspond to relatively high scatter, and high peak areas correspond to δ13C values that are close to the mean of the populations

Summary

Introduction

Fossilizable organic cyst–producing dinoflagellates are ecologically diverse unicellular eukaryotes, and include freshwater and marine, heterotrophic, mixotrophic, autotrophic, and polar and tropical species (Matthiessen et al, 2005). Culturing experiments have shown that dinoflagellate 13C fractionation increases with seawater CO2 concentrations, indicating potential for a CO2 proxy (Hoins et al, 2016b, 2015; Van de Waal et al, 2013). A recently developed analytical setup allows for the analysis of tens of nanograms of particulate organic matter for δ13C (Van Roij et al, 2017). This setup, laser ablation–nano combustion–gas chromatography–isotope ratio mass spectrometry (LA-nC-GCIRMS) has been shown to achieve precise and accurate δ13C values for higher plant pollen (Van Roij et al, 2017)

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